The present invention relates to spark plugs. More particularly, the present invention relates to torch jet spark plugs.
Conventional spark plugs have primarily two functions in an internal combustion engine. The first is to efficiently ignite the fuel/air mixture and the second is to remove the heat out of the combustion chamber. A sufficient amount of voltage must be supplied by the ignition system to cause a spark to jump across the spark plug gap. Additionally, the temperature of the spark plug""s firing end must be kept low enough to prevent pre-ignition, but high enough to prevent fouling of the spark plug.
As disclosed in U.S. Pat. No. 5,421,300 to Durling, et al., a torch jet spark plug is configured to ignite an air/fuel mixture within a combustion pre-chamber formed integrally within the body of the spark plug, such that a jet of burning gases emanates from the pre-chamber and projects into the main combustion chamber of the engine, in order to enhance burning within the main chamber. The torch jet has several electrodes: a first inner electrode (projecting into the pre-chamber); a second inner electrode (located on the internal surface of the pre-chamber forming a gap with the first inner electrode); an outer electrode (formed integral to the second inner electrode); and a ground electrode (formed adjacent to the outer electrode to define an outer spark gap). The inner spark gap ignites the air/fuel mixture that is introduced into the pre-chamber during the engine""s compression stroke. This results in a jet of unburned air/fuel being ejected from an opening at the end of the pre-chamber when the spark plug is fired. The jet passes near the outer spark gap and is ignited by the flame kernel from that gap. The now burning jet carries the flame rapidly and deeply into the main combustion chamber.
The internal electrodes of the torch jet spark plug ignite the air/fuel mixture within the pre-chamber. Conventional materials for spark plug electrodes include a copper core center electrode with platinum tipped center and side electrodes. Since the torch jet spark plug involves the burning of gases within the spark plug pre-chamber, the electrodes are exposed to extreme service conditions (mechanical, chemical, electrical, and thermal conditions) causing erosion and electrode burning.
What is needed in the art is an electrode for spark plugs that is electrically and thermally conductive, corrosion resistant, and high temperature resistant.
The deficiencies of the above-discussed prior art are overcome or alleviated by the torch jet spark plug and electrode composition. The torch jet spark plug electrode composition comprises, based upon the volume of the composition: up to about 75 vol. % of a bonding agent, about 20 vol. % or greater of a catalytically active material, and about 5 vol. % or greater of a transition metal material.
The torch jet spark plug comprises a shell with an insulator body concentrically disposed within at least a portion of the shell. A pre-chamber is concentrically disposed within at least a portion of the shell and at least a portion of the insulator body, the pre-chamber having an orifice disposed at a first end of the pre-chamber and at an insulator body first end. On at least a portion of a pre-chamber internal surface is an inner electrode comprising up to about 75 vol. % of a bonding agent, about 20 vol. % or greater of a catalytically active material, and about 5 vol. % or greater of a transition metal material. At least partially disposed within a second end of the insulator body, opposite the insulator body first end, is an upper terminal. Finally, an upper electrode is disposed within the insulator body, between the inner electrode and the upper terminal, and in a spaced relation to the inner electrode.
The above discussed and other features and advantages of torch jet spark plug electrode will be appreciated and understood by those skilled in the art from the following detailed description and drawings.